Changing the default shell to the system Bash

The default shell on macOS Catalina was changed to Zsh.

To change back to Bash, use the chpass command:

> which chpass
/usr/bin/chpass

Note that instructions elsewhere might say chsh, but the programs are identical:

diff -s /usr/bin/chpass /usr/bin/chsh
Files /usr/bin/chsh and /usr/bin/chpass are identical

(so is chfn).

The standard shells that chpass will allow users to change to (or from), without root permission, are those listed in /etc/shells.

To change:

chsh -s /bin/bash

Then any new terminals will use Bash instead of Zsh.

On macOS a consequence of this change is that the following message is printed every time bash is invoked:

The default interactive shell is now zsh.
To update your account to use zsh, please run `chsh -s /bin/zsh`.
For more details, please visit https://support.apple.com/kb/HT208050.

This can be suppressed by adding:

export BASH_SILENCE_DEPRECATION_WARNING=1

to ~/.bash_profile.

Changing the default shell to Homebrew-installed Bash

The system Bash is old:

> /bin/bash --version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin19)
Copyright (C) 2007 Free Software Foundation, Inc.

but it is possible to install an up-to-date version of Bash using Homebrew, and then default to that.

To do this:

brew install bash

The new Homebrew-installed bash is in /usr/local/bin, which comes before /bin in $PATH, and therefore takes precedence over the system Bash. So now:

bash --version

yields:

GNU bash, version 5.0.18(1)-release (x86_64-apple-darwin19.5.0)
...

which is the newer version installed by Homebrew. However, the default shell is still the system Bash:

> echo $BASH_VERSION
3.2.57(1)-release

The procedure for changing the default shell is as above, except that the new Homebrew-managed shell is not on the "approved" list in /etc/shells, so a user (other than root) can't switch to it. Add it first with:

sudo sh -c "echo /usr/local/bin/bash >> /etc/shells"
chsh -s /usr/local/bin/bash

Note that the echo command is run in a subshell so that the file re- direction works. (Or you could do echo /usr/local/bin/bash | sudo tee -a /etc/shells.)

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